Method of casting brake drums



L Jan m 19394 D. J. CAMPBELL 1,943,720

METHOD 0F cAsJTING BRAKE DRUMS Filed Nov. 2, 1932 iNvENToR ATTORNEY-Patented Jan. 16, 1934 lwl'rlain OFFICE.

I v1,943,720 ME'rnop or' CASTING BRAKE DRUMS Donaldl J. Campbell, SpringLake Township, Ottawa County, Mich., assignor to Campbell, Wyant &Cannon Foundry Company, Muskegon Heights, Mich., a corporation ofMichigan Application November 2, 1932. Serial No. 640,793

6 Claims.

This invention relates to a method of lproducing compound brake drumsfor motor vehicles,

used in conjunction with other braking mechanism for retarding andstopping such vehicles.

The drum is also useful for braking other rotating mechanism.

' It is an object and purpose of the present invention to produce brakedrums of exceptional strength and resistance to fracture, and at thesame time provide a frictional braking surface o f a high degree ofeiliciency. More specifically the invention consists in making a drum asa compound casting, wherein the outer portion is of the proper grade ofcast iron, there being combined the' strength and toughness of steelwith the advantageous braking characteristics of cast iron, it beingagainst an inner cast iron surface that the braking shoes operate.

By reason of the necessity of using va particularly high grade of castiron, one which is firm and dense in structure and the necessity thatlthe same shall be free of pits, blow-holes or the like',

and because of the difliculty in making proper joinder between cast ironand steel over al1 points body of cast iron is relatively small and thethickness of the cast iron band at the inner side of the drum is onlyapproximately three-sixteenths of an inch or even less, the problem o'fproducing such composite joinder of steel and iron is a diflicult oneandv itis only after long experiment and trial that methods of properlyandi` practically producing the same have been perfected.

An understanding of my invention whereby the complete, practical andsuccessful attainment yof the objects above stated are secured, as wellas others not at this time specifically enumerated,

may be had from the following description, taken in connection with theaccompanying drawing,

in which,

Fig. 1 is a fragmentary horizontal central vertical section illustratingan apparatus for centrifugally casting and producing the drum. Also vthemold and a section of the brake drum of my' invention are shown withinthe mold, and

Fig. 2 is a central vertical section of a brakedrum as produced by themethod of my inven/ tion.

Like lreference characters refer to like parts in the figures of thedrawing.

In practicingI the method of my invention, a

suitable apparatus is provided which may be similar in all essentials tothat shown in my prior application for patent, Serial No. 573,949, filed.of contact engagement, particularly where the November 9, 1931. Theparts of the apparatus j illustrated in connection with .the present in'vention comprise a `chuck housing 1, at the -end of a rotatable shaft 2,which is mounted for rotation in4 suitable bearings, not shown. The '30chuck comprises a plurality of jaws, 3, which have inwardly extendingarms'4 pivotally connected -to a head 5 located at the outer end of arod 6.4 Each jaw member 3 has an inwardly extending arm 7 pivotallyconnected to a radial arm 65 8 of a second head secured at the outer endof a hollow shaft 9 which extends through the main shaft 2, rod 6passing through the shaft 9. As shown in my prior application'for patentto which reference is made, this apparatus may be operated to projectand open the jaws 3 of the chuck, or to draw the same inwardly and closethe jaws as they bear against the inner tapered sides of the chuckhousing 1. j

Each ofthe arms 4 of the chuck jaws 3 at its 'f5 inner side is formedwith a flat surface 10, and all of the surfaces 10 on said arms, whenthe chuck is retracted into its housing. provide a back support for amold. The mold 11 preferably is of baked sand similar to that used in abaked sand core, and may be formed Within an outer thin steel or sheetmetal band 12. The mold is of annular cylindrical form and at each endhas an inturned annular iiange 13; and the vback flange 13` of the moldis what vcomes against the 85 surfaces 10 after the mold has been placedin the chuck and the chuck drawn into the housing to the position shownin Fig. 1.

The apparatusdescribed, after the mold 11 has been located within thechuck and the chuck drawn to closed position,l is ready to receivemelted steel which ,forms the outer portion ofthe brake drum. The moldis rotated first at a relatively vslow speed, suiilcient that whenmelted vsteen is placed therein the steel win be distributed bycentrifugal'force evenly over the inner surfaces of the mold and willenter the grooves formed at the inner side of the mold and thus vprovidethe outer shell section 14 of the drum, with ribs 15 integral therewithand extending outwardly entirely around the same, said ribs beingprovided by forming the inner side of thei mold at therst instance 'withsuitable grooves forl reception of the metal. And at each end of theinner portion of the vmold. other grooves are made, such that when themelted steel enters it provides outwardly extending flanges 1'6 ofsteel. The rotative speed of the apparatus, when the steel is depositedand while it is being-centrifugally carried into place, cannot beexcessive as 110 excessive speed would cause a detrimental effect uponthe mold 11 but at a speed or rotation such that the peripheralspeed atwhich the steel is moving is approximately 600 lineal feet per minute,the steel evenly distributes itself under the centrifugal action andtakes a form within the mold whereby it is of substantially uniformthickness except where the grooves are made for thebngesand outwardlyextending ribs descri e The temperature of the steel when introducedinto the mold is very high and may at times reach 3600" F. Thisexcessive temperature is not neeessarily required but the temperature ofthe steel must be such that it is free flowing initially and is uidenough that it will spread evenly over the inner face of the mold andprovide a substantially uniform cross section so far as the steel outerportion is concerned.

After the steel has been poured., andl has thus been uniformlydistributed it is permitted to cool `until its temperature is below themelting temperature of the steel and at such temperature, the steel willbe sufllciently congealed that it will not be penetrated and disruptedby the introduction of the molten iron lining band portion, but is ofv asufilciently high temperature that when the melted cast iron at a properhigh temperature is introduced into the rotating apparatus and the samestepped up in speed of rotation, a compiete fused ioinder of the steeland cast iron will taire place and an integral compound castingproduced.

Cast iron for brake drum purposes has to be oi? e. high quality and,when the drum is nished at its inner surface, present no flaws such aswould come from trapped gas. have no dirt or scale permeating the sameand lbe of a dense and herd quality. Cast iron of this character can beproduced in a cupola furnace and will melt and new freely at 2400 F. butthe temperature of the cast iron must be considerably in excess of thisfreely flowing melting temperature in the present invention. The meltedcast iron is superheated several hundred degrees above its melted freelyflowing stage. That is, in order to get a proper complete-minder of theiron and the previously cast but still a highly heated steel, there is,a superheating of the melted cast iron to 2600" F. and preferably thetemperature will be nearly reti? or 2900 P'.

The apparatus which supports the mold is ro-v tion. A speed of 3500lineal feet per minute of the brake drum will produce a continuoushomogeneous structure of the two metals and the speed may be increasedabove this amount for example as high as 4500 lineal feet per minute.And it is not desired that the lower limit sha be considered strictly as3500 lineal feet per -minute as, depending upon Athe particulartemperatures of the iron and 4steel when the same are brought together,there are variations-in the necessary and essential speeds of rotationsuch that a complete fusion between "the iron and ste'el would beobtainable at a lower rate of speed..Y

The high speed when the cast iron is intro- =a practical standpointnecessary in order that gases, scale, dirt, air and the like may move-inposition.

wardly to the inner face of the cast iron. it being apparent that thedifferential in centrifugalv forces at the outerside of the molten ironas compared with the inner side of the molten iron, the melted ironhaving a limited thickness usually one-eighth to three-sixteenths of aninch, necessarily is small at low speeds and the speed must besufficient to carry the lighter materials such as scale, gas, air andother undesirable material inwardly to the Iinner side of the molteniron; and the temperature of the molten iron must be that such scale,gases, air and the like maypass through the iron while it is still in avery fluid condition, whereby when the` casting is cooled the gaseousmaterials not wanted have escaped at the inner side of the cast iron andthe scale. dirt or products from flux which may be used will evidencethemselves as a scale at the inner side of the cooled cast iron bands 17and which is removed on machining the drum on its inner side to providea smooth braking surface.

In the illustration shown, a double width brake drum is shown asproduced in a single operation, the casting made being divided midwaybetween its two ends to produce two brake drums, one of which is shownin Fig. 2. It is of course apparent that the mold l1. may be providedwith an inwardly extending annular rib half way between the two flanges13 so thatthe two drums may be cast at one operation separate from eachother. This, however. is a detail of apparatus and is not of importancein connection with the present invention which is more concerned in thepractical and successful provision of brake drums in a compound castingof steel and cast iron, the steel at the outer portion and the cast ironat the inner portion, and the steel and cast iron homogeneously,continuously and intimately fused and connected together where the castiron comes against the steel.

Having thus described my' invention, what I claim as new and wish tosecure by Letters Patent is:

l. The herein described method of producing brake drums which consists,in preparing a mold, rotating the mold, pouring molten steel into themold while the same is rotating, cooling the steel until its innersurface is considerably less plastic than the .interior of the bodythereof, pouring melted cast iron into the mold against the steel andthen cooling the metals.

2. A method asset forth in claim l in which the rotation of the mold ismaterially increased during or after the introduction oi the cast ironwhereby centrifugal forces will act thereon to 33@ cause interlockingbetween the cast iron and the inner surface ofthe steel, the plasticinterior of the body permitting such action.

3. A method as set forth in claim 1 in which the cast ironlis heated toa temperature above the inner surface of' the steel whereby the sametransmits heat thereto to soften the same and render it more plastic,such softening action occurring after the `cast iron is in itsconcentric l i 4. The method of producing a composite brake drum whichconsists in preparing a refractory mold4 of comparatiw'elyl weakconstruction, rotating the mold relatively slow, depositing molten steeltherein, said rotation being sumcient tocause equal concentricdistribution of the said molten steel, cooling the said steel to apredetermined degree, pouring molten ironvagainst the steel before thesteel has congealed, and then inl50 creasing the' speed of ythe mold ltocause vsai molten iron to fuse with the steel.

5. A method as set forth in fclaim 4 in which the molten iron issuperheated to a temperature' above the melting point: ot the steel inorder to form a safety factor'.

6. A method of producing a brake drum from two metals having diierentmelting points, said 'alsl metaihaving the higher meltingrpomi: also mwring the greater density, which consists in, providf ing a rotating mold,melting and pouring the cooling the drum.

the mold'and then l DONALD J. CAMPBELL.

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